Background: Few data are available regarding the
natural course of psychiatric symptoms in dementia with Lewy
bodies and Alzheimer's disease. To acquire this information is
essential to inform differential diagnosis and treatment
decisions.

Method: The current study provides prospective
data regarding a representative case-register cohort of patients
with operationalized clinical diagnoses of dementia with Lewy
bodies (N = 82) or Alzheimer's disease (N = 132), with verified
accuracy of clinical diagnosis against postmortem examination.
Psychosis (Columbia University Scale for Psychopathology in
Alzheimer's Disease) and depression (Cornell Scale for Depression
in Dementia) were assessed at baseline and annual follow-up.

Results: Visual hallucinations were
significantly more likely to be persistent in patients suffering
from dementia with Lewy bodies (chi2 = 19.1, df = 1, p
< .0001). Although a number of other psychiatric symptoms were
also more frequent at baseline in dementia with Lewy body
patients, they were not significantly more likely to persist.
Delusions and auditory hallucinations did, however, persist in
more than 40% of patients across both diagnostic groups. Patients
suffering from dementia with Lewy bodies were significantly more
likely to develop new auditory hallucinations over the year of
follow-up (chi2 = 14.4, df = 1, p < .0001).

Conclusion: These results confirm that, although
a number of psychiatric symptoms are common in dementia with Lewy
bodies, it is only visual hallucinations that are significantly
more persistent, with important treatment implications.